Effect of tillage and crop rotation on root and foliar diseases of wheat and pea in Saskatchewan from 1991 to 1998: univariate and multivariate analyses

Disease severity and incidence of fungal species on wheat and pea were evaluated under zero, minimum, and conventional tillage in three rotations with increasing broad-leaved crop diversity from 1991 to 1998 at Indian Head, SK. The objective was to determine whether differences in crop rotation and crop residue at the soil surface would increase crop disease problems. Rotation and tillage had little impact on disease relative to the environment. Reduced tillage did not substantially increase disease severity from leaf spot diseases of wheat or on diseases of field pea. However, the relative importance of root pathogens of wheat was affected; under reduced tillage Bipolaris sorokiniana and Gaeumannomyces graminis decreased, but Fusarium spp. increased on wheat roots. These changes did not affect overall root severity or yield. Rotations had limited impact on wheat disease severity and the prevalence of fungal species, but wheat grown in diversified crop rotations using cereal, pea and flax had consistently higher yields than wheat following wheat. Growing wheat after summerfallow or pea reduced foliar diseases of wheat compared with wheat after wheat. Increased crop diversity in rotations reduced populations of B. sorokiniana, Septoria tritici, and Stagonospora nodorum in wheat leaves and roots, but growing wheat after flax increased the incidence of Fusariumspp. in wheat roots. Key words: Rotation, tillage, root rot, leaf spot, Triticum aestivum, Pisum sativum